One step closer to the optimum solar cell

For the second time in two years, researchers at the Berkeley Laboratory in the US have announced a new solar cell material that may be able to achieve extraordinary efficiency.

But the two materials are very different.

“The only thing the two materials have in common,” said researcher Kin Man Yu, “is that they both try to capture as much of the solar spectrum as possible.”

In 2002, the researchers learned that indium gallium nitride (InGaN) would respond to different wavelengths of light if the proportions of indium and gallium in the alloy were adjusted. Thus it might be possible to create a photovoltaic cell sensitive to the full solar spectrum by stacking multiple negatively and positively doped layers to form several current-producing junctions.

In their latest discovery – what Yu calls “a totally new material concept”- the researchers treat the alloy zinc manganese tellurium (ZnMnTe) in such a way that a single junction of the material may be able to respond to virtually the entire solar spectrum.

“This isn’t a multijunction material,” adds researcher Wladek Walukiewicz, “it’s even more interesting: a multigap material – a single semiconductor with multiple band gaps.”

The researchers believe that a solar cell based on the technology could achieve 50% efficiency or better – far higher than any yet demonstrated in the laboratory.